Stabilo was a suborbital manned vehicle launched from the stratosphere using a solar balloon. The work on this project started at ARCA after the end of the Ansari X Prize Competition.
The tractor engine offers the possibility to place the manned capsule at the rear end of the vehicle, which offers extended abort capabilities.
The tractor engine, generates reaction gases, close to the ship structure for a long period of time, without affecting the ship integrity. This is possible due to the use of hydrogen peroxide as monopropellant.The fuel tank spherical design require that this vehicle to be launched from high altitude with the help of a carrier solar balloon.

Stabilo technical data

Length

19,8 ft

6 m

Diameter

4.3 ft

1.3 m

Launch weight

2,200 lb

1000 kg

Fuel

HP 70%

HP 70%

Vacuum thrust

6,600 lb

3,000 kg

Altitude of engine start

76,000 ft

23,000 m

Max. speed

3,960 ft/s

1,200 m/s

Max. altitude

330,000 ft

100,000 m

Boost phase acceleration

4 g

4 g

Reentry acceleration

- 4.6 g

- 4.6 g

Stages

1+1

1+1

Crew

1

1

Mission 1

Mission 1 was launched on December 2, 2006. A solar balloon (probably the largest at that time) carried Stabilo capsule to an altitude of 48,200 ft (14,700 m).
The launch and recovery went as planned, the capsule avionics and recovery systems performing well.
Mission 1 flight demonstrated ARCA's capability to transport and safely recover a payload from above 85% of the Earth's atmosphere. The flight system traveled 42 mi (68 km) from the launch point.
The event was covered live by the media.

Stabilo 1B

Stabilo 1B is different compared with the initial Stabilo version because of the rocket engine position. Using a pusher engine allows a lower fuel consumption and the possibility to use a hot, high performance rocket engine. The capsule and the fuel tank were nearly identical with the initial version.

Stabilo 1B technical data

Length

19,8 ft

6 m

Diameter

4.3 ft

1.3 m

Launch weight

2,200 lb

1000 kg

Fuel

HP 70%

HP 70%

Vacuum thrust

8,000 lb

3,600 kg

Altitude of engine start

76,000 ft

23,000 m

Max. speed

3,960 ft/s

1,200 m/s

Max. altitude

330,000 ft

100,000 m

Boost phase acceleration

5 g

5 g

Reentry acceleration

- 5 g

- 5 g

Stages

1+1

1+1

Crew

1

1

The flight sequence

The launch
Stabilo was designed to be launched from an altitude of 76,000 ft (23,000m). It would be transported, during an 1h:45min flight under a 12,400,000 ft3 (350.000m3) solar balloon. The launch will be made vertically, through the very thin balloon envelope.

Vertical powered flight
Immediately after the engine start, the vehicle will begin to accelerate on a vertical trajectory. The max. speed will be 3,960 ft/s (1.200 m/s) and the load will be kept around 4g.

Vertical inertial flight
After engine shut-down, the vehicle will climb inertially. Immediately after engine shutdown the capsule will be separated from the rocket booster. The RCS system will command the capsule attitude. The maximum altitude is above 100 km.

Atmospheric re-entry
After apogee, the capsule and booster rocket will start the descent. At low dynamic pressure, the RCS will keep the capsule with the heat shield down. The aerodynamic stability system placed at the top of the capsule will keep the vehicle into vertical position during the atmospheric phase of the reentry.

The rocket booster recovery
The rocket booster main parachute will be extracted from the nose-cone compartment at an altitude of 4.000 m and a speed of 400 km/h.

Capsule recovery
The capsule's main parachute will be extracted at 4.000 m and a speed of about 350 km/h. The landing speed will be kept below 7m/s.

Hardware details

The monopropellant rocket engine
The reaction gases from the reaction chamber are distributed through the four nozzles. The 20° angle lead to a 6% thrust loss. Despite this, our engineers considered that the advantages of a high security of the ship resulting from a tractor engine are more important and the thrust loss could be compensated through a higher fuel quantity and a longer engine run. The reaction is 100% ecological since hydrogen peroxide decomposes in oxygen and hot water vapors.

The fuel tank
The fuel tank is also built from composite materials. The Stabilo fuel tank is pressurized with nitrogen. Another important characteristic is that the engine is placed directly on the fuel tank structure.

The Reaction Control System (RCS)
For attitude control at high altitude Stabilo uses RCS. There are 6 thrusters that use compressed nitrogen.

The capsule
With the capsule placed at the bottom of the ship, the abort sequence has a simple procedure: the crew capsule could be gravitationally separated from the rocket booster and it is recovered with its parachutes. The capsule offers protection for almost the entire flight sequence, even in case of complete equipment failure, structural damage, etc. The capsule is pressurized at 0.8 bars and contains navigation, flight control and life support systems. The access inside the capsule is made through a lateral auto-pressurized hatch which can be opened from both inside and outside. The pilot has a panoramic view through three portholes. After engine stop and capsule release, the pilot could maneuver the capsule with the RCS. At the top of the capsule is placed a parabolic structure used as a stability system for the reentry. This system stabilizes the ship and the workload of the pilot are reduced to minimum.

Mission 2 of Stabilo 1B vehicle was launched from Cape Midia Air Force Base. The team prepared Mission 2 in close cooperation with the Navy, Air Force and Civil Aviation. The carrier balloon and Stabilo vehicles reached an altitude of 12.000 m. After one and a half hours, Stabilo was identified on the sea surface by Navy Saturn ship. The recovery ship was guided by the satellite transmission system and by Air Force radars.